Gyroscopic pendulum



Patented I :July f7, yi936.- 7

UNITED STATES PATENT omc v Germany Application October 6,1934, Serial No. 747,157 lnGe @ctober ld, i933 This invention relates to gyroscopic pendulunis universally suspended in oscillatory crafts and, more particularly, to means for stabilizing a.'A universally v'suspended frame by means oi two gyro-V s Scopes mounted therein.

; Av further object of this invention is the measlurenrient -of the Atrue course and speed of the' craft by said two gyroscopes. This may be efiected by measuring the true speed over rground. 10 by the one of said gyroscopes, and the side slip of the craft in relation to the direction oi its. longitudinal aids by the other of said` two gyroscopes. According to a further feature of this invention, the whole pendulum may be adjustable into the north-south direction by means of a follow-up motor controlled by a compass, or theflike, [if the course is altered. c I

In a preferable .form of the invention, the vtwo gyroscopes are arranged with vertical precession axes in a pendulum frame universally suspended in theoscillatory craft insuch a way that their spinning'axes are horlzontahand at right angles to each other. This result may be effected by constraining the gyroscopes by means of springs .2'5 to zeropos'itions in which the spinning axis of theI one gyro is normally parallel to the northsouth direction while the spinning axis of the other gyroscope is normally parallel to the eastwest direction. If in a well-known manner both gyroscopes are compensated against the influence of the earths rotation, their precession moments will be proportional to the components of the speed of` the craft in the .north-south direction and east-west direction, respectively. Hence' it 351s possible to. determine the rate and the direc tion of Xthe true speed over ground e. g. by geometricv addition of said components.

Further objects and advantages will be apparent from the following description'taken in con- 40 nection with the accompanying drawing in which Fig. 1 isan 'elevation and f y Fig.' 2 a plan view of an embodiment of a f zyrosc'zopic pendulum embodying the invention and attached to, a moving craft in a defined 'rela- -tibn to the axes of the craft.

Fig. -3 shows in elevationjand y Fig. '4' in plan anotherembodiment'whlch adjustable in relation to the craft carrying the,v

Said. embodiment so as to maintain the gyroscope .50 pendulum with its one axis parallel to the north,

south' line, in l' consequence of which the gym- L scopes or-tnis pendulum as regards their spinning axes vwill `be maintained in the north-south line and in the east-west line, respectively.

Fig.-5 is a' plan-"view, von an enlarged mld,

of a detailof the embodiment shown in Figs. 3

and 4, and ,Gis a section on line M oi Fig. 5.

, Referring now to Figs. 1 and 2, R is the so called pendulum-frame, carrying the gyroscopic 5 system and pivoted at zi, zi to the gimbal-ring r, which ring r in turn is pivoted at z2, en to supports' s1 and sa, these supports s1 and sa lying, for instance, on a line parallel to the' longitudinal axis of the craft. The direction of` the longitudinal axis of the craft is that indicated by the arrow P in Fig. 2. The centerxof gravity of the entire pendulum is ata level below the plane of the pivot axes, and the position of said center y i of gravity is determined by a weight K adjustable vertically along a guide R' on the frame R.. The distancev of the centre of gravity of the whole pendulum below the plane of the pivot axes is so vdimensioned aslto give to the pendulous system an oscillation period of only a few minutes, in consequence of which the system will not re- -spond to short-period accelerations due to the oscillations ofY the craft around its longitudinal and its transverse axes.- The said short oscillation period of the system is advantageous especially for gyroscopic penduluxns servingas an artificial horizon 'for oscillatory crafts, since such gyrosco'pic pendulums have to'be ready for op-v eration within a comparatively short time. The housings of the two gyroscopes K1 and Kn are-- pivoted verticallyat c1, cz to the pendulum frame R. The spinning axes ai and az of the two gyroscopes arev arranged horizontally and at practically 4right angles to each other. 'As regards the gyroscope m, the influence ofthe actual .earth '315-4 rotation is compensated in a manner well knownl per se by means of an electro-magnetic coilS pivoted or swinging between the poles of a magnet, generallyaa permanent magnet, as shown Vat M. For instance., the said coil S may be/of the type knowncas a Deprez coil. For the said purpose of compensating the actual earth rota,- tion with respect to-theI g'ylfOScOPe K2, the said coil isU excited by a current, which is dependent on the angular speed of the earth and the angle between the course of the craft and the' meridian and is proportional tothe angular speed ofthe earth as long as the said angle between the course ofthe craft and the meridian. is maintained. It may be noted that the said compensation is known per se as shown by wayof example for instance in United States Patentl No. 1,940,387.

It will be evidentvfrom the above that the gyroscope will not experience a. directive force. ai 'long as' it is 4not displaced in relationtothe 55 earth. However, as soon as the gyroscopic pendulum is moved along with the craft in relation to the earth, the gyroscope K2 will respond to the speed with which the craft moves relative to the earth, which speed in the following may be called the apparent earth rotation. In consequence of the said eect, the spinning axis a2 of the gyroscope K2 will execute a turning movement and take up a position in which it is parallel to the axis of the apparent earth rotation,

i. e. transverse to the direction of the movement executed by the craft relative to the earth. As long as the direction of the said movement of the craft is parallel to the longitudinal axis of the craft, the spinning axis a2 of the gyroscope Ka will be lying in a plane which is at right angles to the direction of the longitudinal axis of the craft. As soon as, however, for any reasons, for instance in consequence of any motion of ythe medium in which the craft travels, the

. direction of the movement of craft relative to the earth is deviated from parallelism with the directionof the longitudinal axis of the craft, the spinning axis a2 of the gyroscope K2 will deviate from its zero position shown in Figs. l and 2 and assume a position in which it includes with the transverse axis of the craft, a'n angle deilned by the line through the pivots 21, zr, the size of which angle will be proportional to the amount of the difference between the direction of the movement of the craft and the direction of its longitudinal axis. This angle, the so-called drift angle, is indicated by an indicator b on a scale b', the indicator being xed to theprecession axis of the gyroscope K2 and the scale b' being provided on the frame R.

It is understood that an indication of the said side-slip or drift angle may also be transmitted to other places in the craft,` for instance to the pilots seat.

As in practice the angle of drift will be com'- paratively small, the gyroscope K2 will always remain able to maintain the elements in a horizontal plane notwithstanding the oscillations of the craft around its longitudinal axis which is, as will be clear from the above, parallel to the k line .2z-22.

As regards the gyroscope K1, the influence of the actual earth rotation is also compensated in a manner known per se, namely by means oi.' a

,spring f connected at its one end to a lever d in full lines) in which the direction of the spring force is identical with the longitudinal direction of the lever-d, no moment is exercised upon the precession axis of the gyroscope K1 by the spring f. By displacing the sleeve e1 on the cirf cular guide e, for instance into the position shown in dotted lines, it is possible to exercise a moment of any desired value on the precession axis of the gyroscope.

The initial value of this moment is, as regards the gyroscope K1, so dimensioned, as to compensate the directive force exerted upon the spinning axis of the gyroscope by the actual earth rotation in case the spinning axis a1 is parallel to the direction of movement of the craft, as is shown in Figs. 1 and 2. The said directive force resulting from the actual earth rotation is, once for all, to be measured in any well-known man-i mapparent earth rotation has to be calculated as ner. This force is dependent on the angle between the course of the craft and the meridian as well as on the linear velocity of the earth in that geographic latitude in which the craft moves. By means of the spring f not only the influence 5 of the actual but also the inuence of a defined amount of the apparent earth rotation may be compensated as regards the gyroscopel K1. To this end, the directive force resulting from the l0 far as the craft travels at its normal speed, i. e. a predetermined value of speed, and the spinning axis a1 of the gyroscope K1 is parallel to the longitudinal axis of the craft. The last mentioned directive force corresponding to a predetermined value of the apparent earth rotation may be compensated by `the same spring l, by which the actual earth rotation is compensated. Accordingly, the gyroscope K1 is totally without any directive force as long as the craft has. that 20 real speed over ground, say 200 km. per hour, for which the compensation was made. Any difference between the vactual speed over ground of the craft'and the predetermined or selected value of speed mentioned above, which difference may 25 be caused for instance by a wind or the like, will'exert a corresponding directive force uponV the gyroscope K1,vwhich directive force will cause a precessionmovement of this gyroscope of such an amount that its spinning axis a1 tends to move into a position in which it is parallel to the direction of thev over-ground movement. A precession of thisamount is, however, prevented by the action of the spring f, which acts against the directive vforce of the gyroscope K1. 'Therefore, the gyroscope will only precess until the tension of the spring is equal to the directive force, by which the gyroscope is moving around its precession axis. The precession angle obtained in this way or, in other words, the deflection of the spinning axis of the gyroscope from its normal position shown in the drawing will therefore be a correct measure for the said difference between th real speed over ground and that value of the relative speed, according to which the compensating moment had been dimensioned. Accordingly the indicator/g fixed to the pivot c1 of the gyroscope K1 will indicate the said difference on the scale g arranged on the pendulum frame R, which scale may be calibrated in degrees of speed.

As long as the craft is moving along a predetermined course, to which end a compass may be used, the spinning axis of the gyroscope K1 will remain accurately or approximately parallel to the direction of this course and accordingly the spinning axis az oi.' the gyroscope K2 will accurately or approximately take up a position at right angles to the said course. Therefore, the iirst named gyroscope 'will stabilize the system 60 in its horizontal position against oscillations of the craft around its transverse axis and the second gyroscope will stabilize the system against oscillations of the craft around its longitudinal axis. When the course is changed, it is necessary 65 to bring the spinning axis of the gyroscope into the new course direction. This is effected by a moment brought into action upon the gyroscopic pendulum about its axis 1 -21. This moment may be generated by a moment generator D which 70 may be of the same character as the compensating device S, M described above, that is to say, it may consist of an electro-magnetic coil pivoted orv swinging between the poles of a permanent magnet. By the inuence of the said turning moment, which is to be manually controlled by the pilot or operator, the axis of the gyroscope K1 will move into the new direction of travel. This moment on the one hand and the positionof the centre of gravity of thlgyroscope K1 in relation to its suspension axis on the other hand are so selected with respect to each other that the precession velocity of the gyroscope K1, with which the spinning axis goes into the new course direction, is exactly equal to the angular velocity of the craft during its movement from the original course into the new course. In thisiway the gyroscope K1 will maintain its position in relation to the pendulum frame R even during a turning of the craft around its vertical axis. Therefore, the pivots c1, c1 will not rotate within their bearings' while the craft is altering its course, for which reason frictional effects altering the adjustment of the gyroscope will not arise in the said case. Y

It may be noted that the precession velocity with which the spinning-axis a1 .of the gyroscope K1 moves into the new course may be made equal lto the angular velocity of the craft ina very simple manner, because in ships as well as in aircraft the air speed in all cases is nearly constant for a certain type and therefore once for all known. The angular velocity atv which the course. alterations take place is independent of the speed over ground; it is only dependent on the air speed, which with suflicient accuracy may be assumed as a constant one.

As the speed of the craft will remain constant even during the change of course, itis .possible to cause the gyroscope K2 to assume a precession velocity which is equal to the angular velocity of craft when the craft is altering its course. The moment which causes the precession movement of the gyroscope K2 during change of the course, results, as is well known, fromthe centrifugal forceacting upon the gyroscopic pendulum while this pendulum or rather the craft is moving along a curved line. This centrifugal moment acts around the line 22-22 of the gyroscopic pendulum and causes a'precession movement of the gyroscope'K2, the direction of which movement corresponds to the direction of the 'travel curve in such a way that the gyroscope K2 will turnv in thesame sense as the craft. The

distance of the centre of gravity below the plane of the two axis ,e1-,a1 and 22-32, which distance may be adjusted by displacing the weight K vertically along the guide R' provided'on the frame R, is so dimensioned that the moment of the centrifugal force lacting upon the centre of gravity, which force is proportional to the angular velocity and to the speed of.r the craft, causes lsuch a precession velocity of the gyroscope vK2 that this gyroscope lwi emain 1n its position in relation to frame Rf Therefore, said dimension of the distance of the centre of gravity the precession velocity of 'the gyroscope K2 4will become .as large as the angular velocity of the craft. In consequence. of this the pivots c2 will be prevented from turning within their bearings; therefore, frictions disturbing .the position of the gyroscope K2 will not arise.v

The precession angles ofthe gyroscopes Ki and K2, being proportional to the difference between the speed over ground vand the normal air speed p and to the drift of aircraft respectively, maybe indicated directly. In a similar manner the angular movements of the pivots a1 and z2 within their bearings, which Vangular movements correspond to the roll and pitch of the craft respectively, may be indicated by indicators u1 andm onfthe scales u2 and v2 respectively the indicators being secured to said pivots 21 and 22. v

In the -embodiment shown in Figs. 3 and 4, the two gyroscopes Kiand K2 are mounted by means of their 'vertical precession-axes c1 and c2 respectively in the frame R, universally mounted in the craft, in the manner already described in relation to Figs. 1 and 2. In this second embodiment, the supports s1 and s2 by which the horizontal pivotsl z2 are carried, are, however, no longer .in a fixed position on the craft; these supports are arranged on a disk L mounted-to turn in a plane parallel'to the base of the craft. A motor moperates a worm i engaging the disk, which can thus be rotated in such a; manner that the pivots a2 will always remain in the north-south direction. For this purpose, the motor m is controlled e. g.

by the needlet of a magnetic compass, said needle' In Fig. 4 the arrow P indicates the .direction t of travel, whilst-the arrow N indicates northsouth direction., vEach gyroscope K1 and K2 is provided with an electromagnetic'device qi and q2 respectively for compensating the directive moment resulting from the rotation of the earth.

This compensation is well known. In consequence of this, the gyroscopes have no directive force as long as the craftis not in motion.

vEach of the devices q1 and q2 may be of the same character asthe moment generator D and the compensator S, M, that is to say, such device may consist of an electro-magnetic coil pivoted or swinging between the poles of a permanent magnet, as shown best in Fig. 2y with respect to the ,compensator S, M. When the craft is travelling in the direction shown by the arrow P, the gyroscopes K1Y andK2 are influenced by a directive moment caused by gravitation. Due to the inuence of said moment, the gyroscopes tend to assume a position in which their spinning axes ai and a2 are transverse to the direction of travel ver ground. The gyroscopes are, however, prevented from assuming said position by springs f1 ,and f1 whose one end is attached to the frame R, as described below and whose other end is attached to a two-armed lever o1 and C2i respectively secured tothe precession axis of each gyroscope. By the springs f1 the spinning axis of the'gyroscope Ki is constrained to the northspeed rate in the north-south direction, whilst the gyroscope K2 is inuenced by? a directive force. proportional to the speed. rate in the eastwcst direction. In consequence of this,"the gyroscope K1 willassume a precession angle corresponding to the-speed rate in the north-south direction and the gyroscope K2 will/ assume a precession angle corresponding to the speedv rate in the east-westdirection. These angles are indicated on the scales g' and b by means of the indicators g and b secured to the precession axes c1, c2 of the respective gyroscopes.

It may be understood thatv the directive force resulting from the rotation of the earth which is to be compensated in the embodiment according to Figs. 3 and 4 is independent of the course relative to the meridian, as the gyroscopes have a fixed position in relation to thc north-south and to the east-west directions.

For a good stabilization of the artificial horizon it is necessary that the spinning axes a1 and az of the gyroscopes will always remain at practically right angles to each other. In order to ensure this, the normally stationary ends of the springs constraining the gyroscopes to a normal zero position, may be mounted for adjustment along ring guides E of the same general character as the one shown at e in Figs. 1 and 2. These ring guides E (like the ring e) are rigid with the frame R, and along them the slides or members E are movable circumferentially, for instance by the rotation of worms journaled on said members'E and meshing with Worm teeth E on the respective ring guides. The shafts of the worms are provided with squared ends for the reception of a suitable operating crank or key. The adjacent ends of the two springs f1 are attached to a stud T on one of saidadjustable members E', while the adjacent ends of the springs f2 are similarly attached to the other member E. Each of said members E' also carries one of the scales g' and b mentioned above. Assuming that, according to a certain speed in the north-south direction, the gyroscope Kr may have a precession angle of about in the counter clockwise direction. If, for instance, the indicator g should be deflected through an angle of 15 from its zero position, the operator will know that he must shift the member E" connected with the springs fi, circumferentially of the ring E, through an angle of 15, in such a direction that the gyroscope K1 will be brought back to its original position relatively to the frame R. That is to say,

.assuming counter clockwise precession of the gyroscope K1, the member E' to which the springs fi are attached will be displaced along the guide E through an angle of 15 in the clockwise direction to readjust the gyroscope K1 into its zero position. At the same time the scale g will be shifted by an angle of 15 along said ring guide E in the clockwise direction, owing to the fact that the member E and the scale g are rigidly connected with each other. Hence, the indicator y will always indicate on its scale the real speed rate in the north-south direction, though the gyroscope may have been readjusted into its zero position. Similar remarks will apply to the indicator b provided for the east-west gyroscope K2.

I claim:

1. A gyroscopic apparatusincluding a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on vertical 'precession axes in .said frame, means for applying ytorques about ing means corresponding to a predetermined normal ground speed of the craft.

2. A gyroscopic apparatus including'a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivotedon vertical precession axes in said frame, means for applying torques about said precession axes-to nullify the influence of earth rotation on each of said gyros, a spring for constraining one of said gyros to a position with its spin axis lengthwise of the craft, a lever fixed to the precession axis of said gyro, said spring being attached at one end to said lever and at its other end to said frame, and means for adjusting the tension of said spring corresponding to a predetermined normal ground speed of the craft.

3. A gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on vertical precession axes in said frame, means for applying torques about said precession axes to nullify the iniluence of earth rotation on'each of said gyros, a spring for constraining one of said gyros to a position with its spin axis lengthwise of the craft, a lever fixed to the precession axis of said gyro, said spring being attached at one end to said lever, a ring guide carried by said frame, and a sleeve adjustable along said guide, the other end of said spring being attached to said sleeve, whereby movement of the sleeve along said guide will change the tension of the spring, to permit such tension to. be adjusted corresponding to a predetermined normal ground speed of the craft.

4. A gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on verticallprecession axes in said frame, an electromagnetic device for applying a torque to the precession axis of one oi said gyros to nullify the influence of earth rotation on such gyro, a lever secured to the precession axis of the other gyro, a spring attached at one end40 to said lever and connected at its other end to said frame, and means for adjusting the tension of said spring corresponding to the inuence of earth rotation and to a predetermined normal ground speed of the craft.

' 5. A gyroscopic apparatus including a "frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on vertical precession axes in said frame, an electromagnetic device for apply-l ing a torque to the precession axis of one of said gyros to nullify the influence of earth rotation on such gyro, a lever secured to the precession axis of the other gyro, a spring attached at one end to said lever, a ring guide carried by said frame,.v

and a sleeve to which the other end of said spring is attached, said sleeve being adjustable along said ring guide to vary the tension of said spring corresponding to the iniiuence of earth rotation and to a predetermined normal .ground speed of the craft. l.

6 vA gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on vertical precession axes in` said frame, means for applying a torque about thel precession axis of one of said'gyros to nullify the influence of earth rotation on such gyro, means for constraining the other gyro to a position with its spin axis lengthwise of the craft and for nullifying the inuence of earth rotation on such second gyro, and an electromagnetic device having a movable member attached to said frame, to exert a moment on said frame so as to maintain the second mentioned gyro in its position relative fis , i 2,046,995' to such frame, when-'the craft is altering-l its course.

7. A gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal lspin axes pivoted on vertical precession axes in said frame, means forv applying torques about said precession axs to nullify theinfluence of earth rotation on each of said gyros, and an electromagnetic device -having .a movable member attached to said frame, to uexert a moment on said frame so as to maintain 'one of said -gyros in its position relative to such frame, when the craft is altering itscourse.

vil. A gyroscopic apparatus'including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin-axes pivoted on vertical precession axes in said frame, lmeans for applying torques about said respectively.

precession axes to nullify the influence of earth rotation on eachv of said gyros and for constraining one of said gyros to aposition with its spin axis lengthwise of the craft, indicators" 'secured to the precession axes of the respective gyros, and scales carried by lsaid frame and co-operating with said indicators to, in dicatedrift and speed 9. Agyroscopic apparatus-including a frame,

'.'means pendulously' and universally-mounting said frame on a craft, suchuniversal mounting having one pivot' axis lengthwise of the craft and the other athwartship, two gyroscopes. with horizontal spin axes pivoted on vertical precession axes in said frame, means for applying torques about saidprecession axes to nullify the inuence of earthrotation en ;eachjof said'fgyros and for maintaining the lspin axeslof saidgyroscopes at right angles to each other, and two indicating devices co-operating withfsaid longitudinal and4 transverse pivots of said universal' mounting, to

indicate pitching and rolling angles vof the craft respectively.

; 10. A`gyroscopic apparatus including a frame;

a rotatable member mounted on a craft, means pendulously and universally mounting said frame on said member, vtwo gyroscopes with horizontal spin axes pivoted on vertical precession axes in ,said frame, means for applying torques about said precession axes' to nullify the influence of earth rotation on each of said gyros, means for maintaining the spin axes of said 4g-yros at right angles to each other, a motor for turning said member relatively to said craft, and acompass controlling said motor for automatically maintaining the prientation of said; member when the craft'. is altering its course.

11. A gyroscopic apparatus including a frame, a rotatable member mounted on a'craft, means pendlouslyand universally mounting said frame on said member, two gyroscopes with horizontal mutually normal spin axes pivoted on vertical precession axes in said frame, means for applying torques about said precession axes to nullify theinfluence of earth rotation on each of said gyros, means for maintaining the spin axis of one gyro in axis of-,the other gyro in the east-west direction,

' said means comprising a motor for turning said member relatively to said craft', and a compass controlling said motor forautomatically maintaining the orientation of said member when the craft is altering its (course.

12,'A gyroscopic apparatus including a iframe, a rotatable member mounted on a craft, means pendulously and universally mounting said frame course.

a'torque-about theprecession axis of at least one the north-south direction and [the spin on said member, two gyroscopes with horizontal spin axespivoted onvertical precession axes in s. said frame, .means for applying torques about said precession axes to nullify the influence of earth y rotation on each of said gyros, levers secured to 5 the precession axes of the respective gyros, springs for constraining the spinaxes'of the gyros to north-south and; east-west directions respectively, eachlspring being attached ati one yend tota .respective lever andat the other end to said lo frame,- a motor for turning said member relatively to said craft, and'a compass controlling said mot-orfor automatically maintaining the orientation of `said member when the craft is altering its l5 13.*A gyroscopiolapparatus including a frame, a rotatable 'member mounted on-acraft, means pendulously and universally mounting said-frame onv said'member, two .gyroscopes with horizontal ,spin axes pvoted on vertical precession axes in 20 said frame,- means for applying torques about said precession axes to nullify the inuence of earth rotation on each of saidgyros, levers secured to the precession axes i of the respective gyros, 1 springs for constraining the spin axes of the gyros 25 to mutually normal positions relatively to said frame-each spring being attached at one end to a respective lever Aand at the-other end to said frame, indicators secured to the precession axes of the respective gyros, scales on the said frame, 30

so-operating with said indicators to indicate speed, a motor for turning said member relatively to said craft, and a compass controlling said motor for automatically maintaining the orientation of said member when the craft is altering its course. A14:. A gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on avcraft, two gyroscopes with horizontal spin axes pivoted on vertical precession axes in said frame, means for applying torques about said precession axes to nullify the influence oli earth rotation on each of said gyros, and means for yieldnglyconstrainin'g atleast one .of said gyros vto a definite position of its spin axis relatively to said frame, said means being connected to the precession axis of lsaid gyro and to said frame. l5. A gyroscopic apparatus including a frame, means pendulously and universally mounting said frame on a craft, two gyroscopes with horizontal spin axes pivoted on vertical precession axes in said frame, and means for applying torques about the vprecession axis of each of the gyros to nullify the influence of earth rotation on said gyros, and

of thegyros to lyieldingly constrain this gyroto 55 a definite zero position of its spin axis relatively to said frame, said zero position being so selected Ithat the spin axisof one of the gyrus in vits zero position is at an angle to the spin axis ofthe so other gyro. 16. A gyroscopic apparatus )as claimed in claim' 15, in which the spin axis Q1' the one gyro in its zero position is at right angles to the spin axis of the Aother gyro-in its zero position. t5 1'7. A gyroscopic' apparatus including a frame, means pendulously and 'universally `mounting said frame on a craft, two gyrosco'pes' with horizontal spin axes pivoted on vertical precession.V

g axes in said frame,l and means for applying 70 mined normal ground speed.

18. A gyroscopic apparatus including a frame, a rotatable member mounted on a. craft, means pendulously and universally mounting said frame on said member, two g'yroscopes with horizontal spin axes pivoted on vertical precession axes in said frame, means for applying torques about the precession axes of saidgyros to nullify the in-A 61 2,046,998 direction of the crafts movement at apredeterfluence of earth rotation on said gyros and furthermore such torques about the precession axes 0f said gyros that their spin axes normally are at an angle to each other, a motor for turning said member relatively to said craft, and a compass controlling said motor for automatically maintaining the orientation of said member when the craft is altering its course.

JOHANN MARIA BOYKOW. 

